Gerotor type motor with pressure biased rotary valve

ABSTRACT

The invention relates to a gerotor type rotary piston machine. The casing has a main axis and the gerotor gear set includes an externally toothed star member which is rotatable about its own axis and orbital about the casing main axis. A main drive shaft is rotatable about the casing axis and a universal type wobble shaft connects the main shaft to the gerotor star member. An annularly shaped valve is mounted in said casing for rotation about the casing main axis. The valve is in surrounding relation to the wobble shaft and is driven by the wobble shaft. An annularly shaped pressure plate which is nonrotatable but is capable of a small amount of axial movement is positioned behind the valve. The pressure plate is biased against the valve by pressurized fluid from the inlet port to provide sealing for both sides of the valve. Sealing rings are provided at the rear of the pressure plate betwen it and the casing to prevent leakage from the high pressure inlet regions to the low pressure outlet regions.

United States Patent 1 Sturlason et al.

[ 1 GEROTOR TYPE MOTOR WITH PRESSURE BIASED ROTARY VALVE [75] Inventors:Leif Viggo Sturlason; Carl Verner Ohrberg, both of Nordborg, Denmark[73] Assignee: Danfoss A/S, Nordborg, Denmark [22] Filed: June 14, 1973[21] Appl. N0.: 369,928

[30] Foreign Application Priority Data Primary Examiner-John J. Vrablik5 7 ABSTRACT The invention relates to a gerotor type rotary pistonmachine. The casing. has a main axis and the gerotor gear set includesan externally toothed star member which is rotatable about its own axisand orbital about the casing main axis. A main drive shaft is rotatableabout the casing axis and a universal type wobble shaft connects themain shaft to the gerotor star member. An annularly shaped valve ismounted in said casing for rotation about the casing main axis. Thevalve is in surrounding relation to the wobble shaft and is driven bythe wobble shaft. An annularly shaped pressure plate which isnonrotatable but is capable of a small amount of axial movement ispositioned behind the valve. The pressure plate is biased against thevalve by pressurized fluid from the inlet port to provide sealing forboth sides of the valve. Sealing rings are provided at the rear of thepressure plate betwen it and the casing to prevent leakage from the highpressure inlet regions to the low pressure outlet regions.

3 Claims, 1 Drawing Figure GEROTOR TYPE MOTOR WITH PRESSURE BIASEDROTARY VALVE The invention relates to a rotary piston machine with aninternal splined shaft and wherein an internally toothed ring fast withthe casing engages a rotatable externally toothed wheel which is coupledwith a disc shaped rotary slide so as to rotate therewith, the rotaryslide being disposed between a plate having axial ducts and a part ofthe casing, which plate and casing part are held in spaced. relationshipby a ring on the casing, which ring surrounds the rotary slide.

Machines of this kind operate as pumps or motors. Since the cycle offilling and emptying the displacement chambers formed between thetoothed wheel and the toothed ring proceeds at a greater speed than thatat which the main shaft rotates, the machine has as a pump a largedelivery volume and as a motor a large torque. The valve platecooperates with the plate having ducts as a distributor valve in orderto supply pressurized fluid to the displacement chambers and todischarge it therefrom in the correct sequence, despite the slow speedof revolution of the rotary slide. For this purpose the rotary slidegenerally has valve openings, the number of which is equal to twice thenumber of teeth on the toothed wheel, whereas the plate having ductscontains valve openings which cooperate with the aforementioned valveopenings and the number of which is equal to the number of teeth on thetoothed ring.

ln a known construction (German Pat. application Ser. No. 1,931,143, aslaid open), the rotary slide is inserted between the plate having ductsand the casing part, in a sliding fit. At higher pressures however therearises the danger of a slight increase in the size of the gap betweenthe plate having ducts and the casing part, particularly as a result ofelastic stretching of the axially extending fixing screws. Consequently,gaps of increased size are created between the rotary slide and theplate having ducts and the casing part respectively, and leakage fluidcan pass along these gaps. The quantity of leakage fluid increases withthe third power of the width of gap. This is particularly troublesome inthe case of the rotary slide since the openings at which differingpressures obtain are located very closely to each other.

The object of the invention is to provide a machine of the abovedescribed kind in which the leakage losses occurring at the rotary slidecan be kept very small.

According to the invention, this object is achieved by providing betweenthe rotary slide and the casing part a pressure plate which isnon-rotatable but axially displaceable and which has supply anddischarge ducts and, on that of its faces remote from the rotary slide,a limited annular surface which communicates with the pressurized port.

In this construction, the pressure plate is acted upon by an axial forcewhich is equal to the product of the area of the annular surface and theworking pressure of the machine. Consequently, the pressure plate ispressed against the rotary slide, and the rotary slide against the platehaving ducts. The gaps between these parts can therefore be kept smalland the leakage losses can be kept correspondingly low. As the workingpressure rises, the pressure-applying force also increases, so thatsubstantially constant conditions are achieved over the entire workingrange. The pressure plate of course covers that end face of the rotaryslide remote from the plate having ducts; however, since thenon-rotatable pressure plate is provided with supply and dischargeducts, the supply to the rotary slide is not impaired.

It is particularly advantageous if the annular surface adjoins anannular distributing channel which supplies one set of valve openings inthe rotary slide. Since the one set of valve openings and therefore alsothe associated annular distributing channel must in any case communicatewith the pressure port, this arrangement results in the annular surfacebeing supplied with pressurized fluid in a very simple manner.

In very many cases a rotary piston machine can be driven in both rotarydirections, and this means that one or other of the ports can beselectively used as the pressure port. Assuming that this is so, anextremely simple construction is obtained if two concentric annularsurfaces are present on that face of the pressure plate remote from therotary slide, thoseannular faces being separated from each other by anO-ring and each of them extending from an annular distributing channel,the channels each communicating with a port. It has been found that itgenerally suffices to use one half of the end face as the pressuretransmitting annular surface, so that both annular surfaces are locatedon that face of the pressure plate remote from the rotary slide.

In a preferred embodiment, one of the annular distributing channels isof the end face and the other at the peripheral surface of the pressureplate in the housing part. In this arrangement, one of the annularsurfaces can extend to the outer edge of the pressure plate and thisresults in good utilization of space. Furthermore, two annulardistributing channels of relatively large cross section can beaccommodated in the casing part.

Preferably at least one set of the supply and discharge ducts in thepressure plate is formed by an annular aperture which is divided byaxial partitions. The partitions make it possible for the pressure plateto be a one piece element despite the presence of the aperture. Thesepartitions can also contribute towards the application of pressure tothe pressure plate if they extend to the face of the pressure plate thatis presentedto the rotary slide. To ensure correct operation they shouldthen however be disposed opposite the mouths of the axial ducts in theduct plate.

The invention will now be described in greater detail by reference to apreferred embodiment illustrated in the annexed drawing which shows alongitudinal section through a rotary piston machine in accordance withthe invention.

The casing consists of an end plate 1, a casing part 2, a duct plate 3,a toothed ring 4, and a further end plate 5, these elements beinginterconnected by means of screw bolts 6, 7 and 8, and the gaps betweenthem being closed with the aid of O-rings 9, 10, 11 and 12. A main shaft13 is mounted in the casing part 2 by means of a roller bearing unit andin the duct plate 3 by means of a plain bearing. A sealing element sealsoff the zone through which the main shaft 13 projects from the casing. Acavity 14 in the main shaft 13 accommodates a universal joint shaft 15.The coupling head 16 of this shaft meshes with teeth 17 in the mainshaft 13, and a further coupling head 18 of the shaftmeshes with teeth19 on a wheel 20 which, by means of teeth in the form of cylindricalrollers 21, meshes with the toothed ring 4, displacement chambers beingformed between the teeth of the wheel and those of the ring 4. The outerperiphery of the main shaft 13 carries keys 22 which engage in axialgrooves 23 in a disc shaped rotary slide 24 and drive this slide.

The casing part 2 has an annular extension 25 which in addition tosurrounding the rotary slide 24 also surrounds a pressure plate 26,which is prevented from rotating by pins 27 but can move slightly in theaxial direction. Also provided in the casing part 2 are two ports 28 and29. The port 28 communicates with an annular distributing channel 30,and the port 29 with an annular distributing channel 31. The annulardistributing channel 30 extends along the face of the pressure plate 26,and the annular distributing channel 31 along the outer circumferentialsurfaces of this pressure plate 26 and the rotary slide 24. Two O-rings32 and 33 define a first annular surface 34 which communicates directlywith the annular distributing channel 30. Disposed outwardly of theO-ring 33 is a second annular surface 35 which extends to the outercircumference of the pressure plate 23 and communicates directly withthe annular distributing channel 31. The pressure plate has supply anddischarge ducts 36 and 37. These are formed by an annular aperture whichis divided by axial partitions 38. These partitions extend to that faceof the pressure plate presented to the rotary slide 24 and are disposedwhere the oppositely positioned face of the duct plate 3 is notinterrupted. The same applies in the case of the ducts 36 which begin atthe periphery of the pressure plate and likewise have partitions 39.

The rotary slide 24 has valve passages 40 and 41 which communicatealternately with the annular distributing channel 30 and the annulardistributing channel 31. The number of these passages is equal to twicethe number of teeth on the wheel 20. They form valve openings whichcooperate with corresponding valve openings of axial ducts 42 in theduct plate 3. The number of these axial ducts is equal to the number ofteeth on the ring, and each terminates at the outer part of a gapbetween two teeth fixed in the casing.

if the machine is operated as a motor and is supplied with pressurizedfluid through the port 28, the annular surface 34 transmits pressure.The force thus applied to the pressure plate 26 presses the latteragainst the rotary slide 24 and presses this slide against the ductplate 3. The gaps between these parts are therefore kept small. Ifpressurized fluid is passed to the port 29 when the direction ofrotation is changed. the annular surface 35 transmits the pressure. Theannular surface 35 is approximately as large as the annular surface 34and likewise leads to compression of the pressure plate 26, the rotaryslide 24 and the duct plate 3.

We claim:

l. A gerotor type rotary piston machine comprising a casing having amain axis, expansible chamber means having cyclically movable chamberforming means, r0- tatable shaft means connected to said chamber formingmeans, an annularly shaped valve mounted in said casing for rotationabout said main axis, said valve being in surrounding relation to saidshaft between the opposite ends thereof, fluid passages in said casingbetween said valve and said expansible chamber means, drive meansconnecting said rotatable shaft means and said valve in drivingrelation, said valve having first and second sets of circumferentiallyextending and alternately arranged inlet and outlet ports cooperablewith said casing passages, said second set of valve ports being spacedfrom the inner and outer circumferences of said valve, an annularlyshaped pressure plate in abutting engagement with said valve, saidpressure plate being rotationally fixed relative to said casing andaxially movable relative to said valve, said pressure plate having firstand second fluid passage means having fluid communication with saidfirst and second sets of valve ports, said second fluid passage meansbeing spaced from the inner and outer circumferences of said pressureplate, first and second annularly shaped channels in said casing havingrespectively fluid communication with said first and second pressureplate fluid passage means, said second annularly shaped channel havingthe mouth thereof in radial registration with said second fluid passagemeans, said pressure plate having first and second surface portionsrespectively radially inwardly of said first and second annular channelswith at least one of said surface portions being subjected topressurized fluid in either of said annular channels to axially biassaid pressure plate into abutting engagement with said valve.

2. A gerotor type rotary piston machine according to claim 1 whereinsaid first set of valve passages has the form of recesses relative tothe periphery of said valve.

3. A gerotor type rotary piston machine according to claim 1 whereinsaid pressure plate first fluid passage means has the form of recessesrelative to the periphery of said pressure plate.

l l= l

1. A gerotor type rotary piston machine comprising a casing having amain axis, expansible chamber means having cyclically movable chamberforming means, rotatable shaft means connected to said chamber formingmeans, an annularly shaped valve mounted in said casing for rotationabout said main axis, said valve being in surrounding relation to saidshaft between the opposite ends thereof, fluid passages in said casingbetween said valve and said expansible chamber means, drive meansconnecting said rotatable shaft means and said valve in drivingrelation, said valve having first and second sets of circumferentiallyextending and alternately arranged inlet and outlet ports cooperablewith said Casing passages, said second set of valve ports being spacedfrom the inner and outer circumferences of said valve, an annularlyshaped pressure plate in abutting engagement with said valve, saidpressure plate being rotationally fixed relative to said casing andaxially movable relative to said valve, said pressure plate having firstand second fluid passage means having fluid communication with saidfirst and second sets of valve ports, said second fluid passage meansbeing spaced from the inner and outer circumferences of said pressureplate, first and second annularly shaped channels in said casing havingrespectively fluid communication with said first and second pressureplate fluid passage means, said second annularly shaped channel havingthe mouth thereof in radial registration with said second fluid passagemeans, said pressure plate having first and second surface portionsrespectively radially inwardly of said first and second annular channelswith at least one of said surface portions being subjected topressurized fluid in either of said annular channels to axially biassaid pressure plate into abutting engagement with said valve.
 2. Agerotor type rotary piston machine according to claim 1 wherein saidfirst set of valve passages has the form of recesses relative to theperiphery of said valve.
 3. A gerotor type rotary piston machineaccording to claim 1 wherein said pressure plate first fluid passagemeans has the form of recesses relative to the periphery of saidpressure plate.